Probable cause
The failure of the power turbine thrust (No. 5) bearing due to overheating as a result of oil starvation, which led to the engine failure. Also causal to the accident was an undocumented repair to the gearbox cover oil delivery tube port during which an insert was threaded into the oil delivery tube port that subsequently restricted the oil flow to the power turbine thrust bearing.
NTSB analysis
The commercial pilot and two flight crewmembers were conducting a search and rescue mission for a local sheriff's department in the helicopter. The pilot reported that, after flying five or six lines of the search grid and while in a right turn to begin flying another line of the grid, the engine noise changed. Immediately thereafter and while the helicopter was 200 ft above ground level, the engine chip detector light illuminated, followed by a full authority digital electronic control degrade light. The pilot started to descend toward an open snow-covered meadow for landing, but the engine rpm degraded, so he initiated an autorotation. The helicopter touched down with little forward airspeed and bounced, and the left skid then became caught on an object under the snow. The helicopter rolled onto its left side and then came to rest.
A postaccident examination of the engine showed that the engine gas producer and power turbine drive train had continuity, but there was resistance to the gas producer and scraping of the power turbine when rotated. Further examination of the engine revealed that the gearbox cover had been modified by a repair, which included an insert being threaded into the oil delivery tube port. The insert was blocking the oil flow to the power turbine thrust (No. 5) bearing, which resulted in the bearing overheating and failing due to the lack of lubrication and the subsequent engine failure. No records were found regarding any repair to the gearbox cover oil delivery tube port.
Text from the NTSB. Open the NTSB docket for CEN14FA232 for the full record.
Event
- Date
- May 3, 2014
- Type
- Accident
- Place
- Telluride, Colorado
- Highest injury
- None
- Weather
- Visual (VMC)
- Light
- Day
Bell 407
- N-number
- N407MH
- Category
- Helicopter
- Year built
- 1997
- Damage
- Substantial
- Operating rule
- Part 135 (charter and commuter)
From the NTSB aviation accident database: N-registered aircraft, events since 2008, data through Oct 28, 2026. The file is published monthly, so the latest weeks are incomplete and recent records can change. The official source is the NTSB aviation investigation search. CheckAero is independent and not affiliated with the NTSB.